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Seoul, Korea, december 3rd, 2015
Nico H. J. Pijls, MD, PhD
Catharina Hospital,
Eindhoven, The Netherlands
Imaging & Physiology Summit
PITFALLS IN FFR, iFR, CFR, IMR MEASUREMENTS
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Speaker’s name: NICO H J PIJLS
I have the following potential conflicts of interest to report:
Research contracts : St Jude Medical Consulting: St Jude Medical, Boston Scientific,Opsens
Employment in industry
Stockholder of a healthcare company: Philips, GE, ASML, Heartflow
Owner of a healthcare company
Other(s):
I do not have any potential conflict of interest
Potential conflicts of interest
x x
x
x
IPS Korea 2015
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RECOGNIZING PITFALLS DURING CORONARY
PRESSURE MEASUREMENTS
Part 1: “technical pitfalls”, related to practicalities
during the procedure
avoidable by practical tips & tricks and skills
related to introducer, drift, guiding catheter,
wire manipulations, practicalities of hyperemia
Part 2: “physiologic” pitfalls & interpretation errors
(avoidable by knowledge of physiology)
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First a few practical tips to optimize your technique:
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OPTIMUM FFR TECHNIQUE: catheters
Guiding or diagnostic catheter ? 6F or smaller ?
• FFR has been measured by 5F diagnostic catheters
• but: - more difficult steering/wire manipulation
(because diagnostic catheter lacks inner coating)
- damping of aortic pressure signal due to
smaller lumen
I advice to use guiding catheter
(changing catheter is less cumbersome than
long manipulation with wire or suboptimum
Signal)
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OPTIMUM FFR TECHNIQUE: manipulation of PW
How to prepare and manipulate the pressure wire
• short curve of 45-60 degree
• use the pressure wire with a torquer (cf Sion wire),
i.e. true steering
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Most common pitfalls :
• drift of the signal
• introducer
• pitfalls associated with guiding catheter
• insufficient hyperemia
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Normal resting signal :
• Almost no systolic
gradient
• small or moderate
diastolic gradient
Hyperemia:
• also systolic
gradient
• much larger
diastolic gradient
drift:
• parellel signals
• diastolic notch
remains visible
hyperemia drift resting
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OPTIMUM FFR TECHNIQUE: decrease of drift
How to decrease (apparent) drift
• after equalization (sensor at the tip of the guiding
catheter), wait for 20-30 seconds for stabilization
(small air-bubbles in sensor cavity are flushed away)
• if there is some apparent drift at the end of PCI,
did you measure with the introducer before and
without it afterwards ? (difference 3-10 mmHg)
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Drift in the different pressure wires:
Electronic wires:
• St Jude Medical: < 7 mmHg / hour
• Philips/Volcano: < 30 mmHg / hour
New fiberoptic wires:
• Opsens (Optowire): ~ 0 mmHg
• Acist (Navvus): ~ 3 mmHg /h
• Boston Sc (Comet) : ?
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Resolution of resting vs hyperemic measurements
• The intrinsic error in FFR measurement with electronic guidewires (St Jude Medical, Volcano) is 0.01-0.02
• the total hyperemic pressure gradient within a coronary
artery, is generally 2-3 x higher than the resting gradient.
• Therefore, the accuracy of resting measurements like iFR
(signal-to-noise ratio) is more affected by drift
• Consequently, the relative error of iFR or Pd/Pa at rest,
is 2-3 x higher than with hyperemia / FFR
• in a similar way, the resolution of the pull-back recording is
2-3 x lower with iFR compared to FFR
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-6.00
-4.00
-2.00
0.00
2.00
4.00
6.00
1
Present SJM Aeris wire:
Next generation aeris wire (PressureWireX)
1 hour
0
6 mm Hg
-6 mm Hg
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Most common technical pitfalls :
• drift of the signal
• introducery needle
• pitfalls associated with guiding catheter
• insufficient hyperemia
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Introduction of a “thin
introducer” into the valve of
the ‘Y’ connector
Introduction of a “larger
introducer” in the valve of the
‘Y’ connector
Introducer effect (mistake in live case in PCR 2014!)
Specifically important when pre-PCI assessment was
with introducer and post-PCI assessment without it
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Most common technical pitfalls :
• drift of the signal
• introducery needle
• pitfalls associated with guiding catheter
(especially important in assessment of ostial lesions)
• insufficient hyperemia
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pitfalls associated with guiding catheter
• avoid wedging
(deep engagement during measurement)
• special caveat with sideholes
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50% Area Stenosis
2. Wedging of the Guiding Catheter
7 F Guiding Catheter
3 mm RCA
Recent study by Belgian Group
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Influence of guiding catheter on FFR in case of narrow ostium
vdP13-04-48
use i.v. adenosine and dislodge guiding during measurement
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engagement of guiding
into ostium
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FFR and Guiding catheter with Sideholes
Pd
Pc
Pa
Pressure recorded by guiding
Pa Pc =
When wedging of the catheter or guiding cath with sideholes,
dislodge guiding from ostiumduring the measurement
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Side Holes
Sensor proximal to side holes
Guiding Catheter With Sides Holes
Position of the sensor
Equalization proximal to the
sideholes
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Guiding Catheter With Sides Holes
Side Holes
Sensor in the
proximal RCA
Side Holes
Sensor in the proximal RCA + hyperemia
Position
of the
sensor
12 mmHg
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Coronary Pressure: Pittfalls and Artifacts:
If there is “damping” , small ostium, or if you
are using guiding catheter with sideholes:
use i.v. adenosine and withdraw guiding
slightly from ostium during measurement
(often most convenient by pushing up the PW)
Note: also i.v. regadenoson bolus enables reliable
interrogation of ostial stenosis
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PressureWire in LAD, guiding catheter dis-engaged
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hyperemic pressure pull – back curve
left main ostium LM
( i.v. adenosine, guiding out of ostium)
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A LAST PITFALL ASSOCIATED WITH GUIDING
CATHETER (especially at end of procedure and easily
Interpreted as drift of the PW) :
• pressure artifacts by the guiding
vigorous flushing
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Capillary forces in guiding catheter
meniscus
sometimes capillary forces
result in misregistration of
pressure by the guiding
up to 10 mm Hg
in procedures without pressure
wire, this remains unnoticed
vigorous manual flushing of
the guiding with 5-10 cc of
saline, might restore true aortic
pressure
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MAXIMUM HYPEREMIA IS OF IMPORTANT
Insufficient hyperemia
Importance of Maximum Hyperemia (1):
Underestimation of gradient
Overestimation of FFR
Underestimation of stenosis severity
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Moderate gradient at rest
Moderate increment at hyperemia
Small gradient at rest
Large gradient at hyperemia
ΔP = f.Q + s.Q2
50% ostial left main stenosis 70% long prox LAD stenosis
iFR = 0.89 FFR = 0.85 iFR = 0.94 FFR = 0.57
f = friction coefficient s = separation coefficient
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PressureWire in RCA in 46-year old male
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RCA
resting hyperemia (i.v. adenosine)
pullback - advance - etc
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Hyperemia necessary ?
In general:
• small perfusion territory, distal stenosis, older
patient, moderate long lesion, small artery,
microvascular disease:
often moderate gradient at rest with little
increase at hyperemia
• large perfusion territory, proximal stenosis, young
patient, short severe lesion, large artery, intact
microvasculature:
often minimal gradient at rest with large
increase at hyperemia
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OPTIMUM FFR TECHNIQUE: hyperemia mandatory?
Realize that:
• resting indices poorly predict hyperemic
measurements
• diagnostic accuracy decreases to 80%
Verify study, N=200, prospective and consecutive Resolve study, N=1600, retrospective
Advise-2 study, N = 650, prospective
Contrast study, N= 750, prospective
• pullback recording is time-consuming and has
poor resolution without hyperemia
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Tru
e p
osi
tive
s (%
)
False positives (%)
0% 0%
20%
100%
80%
60%
40%
100% 20% 40% 60% 80%
contrast = 0.93*
Pd/Pa = 0.874
iFR = 0.879
* = larger AUC (p
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100 % certainty (holy grail)
angiography
resting Pd/Pa, iFR,
FFR
70 %
80 %
>95 %
hyperemia
resting indexes
Correct Classification of Ischemic Stenosis
angio
Contrast cFFR 85 %
Simple paradigm:
“the more hyperemia,
the higher the accuracy”
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MAXIMUM VASODILATORY STIMULI
• PAPAVERINE i.c. (12 mg RCA, 20 mg LCA)
• ADENOSINE i.c. (100 µg RCA, 200 µg LCA)
• ADENOSINE i.v. ( 140 µg/kg/min)
• ATP i.c (idem adenosine)
• ATP i.v. (idem adenosine)
• regadenoson (400 µg as i.v. single bolus)
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A few words about i.v. adenosine:
Do fluctuations occur? Yes, in 40 % of patients
Are they a problem? No, not at all !
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CAVEAT:
Resolution of resting vs hyperemic measurements
also the resolution of the pull-back recording is
2-3 x lower with iFR (“iFR-scout”) compared to FFR
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oct 29th, 2014 oct 29th, 2014
Male, 65-year-old, typical angina,
inferolateral reversible defect at MIBI-SPECT
70% lesions in proximal & distal dominant LCX
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distal proximal
resting adenosine 140µg/kg/min
hyperemic pullback recording:
rapid, reliable, detailed information within seconds
65 seconds
48 mmHg 27
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iFR 0.90 iFR 0.89 iFR 0.95 iFR 0.99
“resting” pullback recording with multiple iFR:
time-consuming, less reliable, less detailed information
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iFR 0.90 iFR 0.89 iFR 0.95 iFR 0.99
Blowing up
the scale
does not
add more
information
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7 mmHg
iFR Scout : blowing up the scale does not improve precision !
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100 % certainty (holy grail)
angiography
resting Pd/Pa, iFR,
FFR
70 %
80 %
>95 %
hyperemia
resting indexes
Correct Classification of Ischemic Stenosis
angio
Contrast cFFR 85 %
Simple paradigm:
“the more hyperemia,
the higher the accuracy”
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RECOGNIZING PITFALLS DURING FFR
MEASUREMENTS
Part 1: “technical pitfalls”, related to practicalities
during the procedure
(avoidable by practical tips & tricks and skills)
related to introducer, drift, guiding catheter,
wire manipulations, practicalities of hyperemia
Part 2: “physiologic” pitfalls & interpretation errors
(avoidable by knowledge of physiology)
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Misinterpretation of correct signals:
high FFR and (apparently ! ) severe stenosis:
• small perfusion territory, old infarction
• abundant collaterals
• deceiving angio, look for other culprit lesion !
Diffuse disease:
detectable by hyperemic pullback recording
Severe Microvacular Disease: • IMR, CFR
• Absolute flow and Resistance measurement by new technique
(keynote lecture tomorrow afternoon 2 pm)
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• Nothing is perfect, not even FFR….
• …..but false positive or false negative FFR is
extremely rare
• However, some pitfalls must be recognized and
avoided.
• In most cases of presumed “false negative FFR”,
there is either a technical, physiological, or
interpretational point explaining the case
IN SUMMARY: